In this list, Japanese is listed as rank 5 with asterisk which means more difficult than other languages within the rank 5. It means FSI thinks Japanese is the most difficult language for English speakers to learn.

This is the reason why I respect the Japanese learners who challenge the thick and high wall of language between Japanese and other languages.

And remember that the thickness and the height of wall are the same for the Japanese who learn English.

But we have established education system for English and many loan words from foreign languages which make English environment for Japanese.